Preparing cotton material with improved tensile strength retention properties

ABSTRACT

COTTON FIBRES OR ROVINGS OR SILVERS ARE SUBJECTED TO THE ACTION OF SWELLING AGENT WITHOUT TENSION BEING EXERTED ON THEM. THE SWELLING AGENT SHOULD BE CAPABLE OF TRANSFORMING THE MATERIAL INTO CELLULOSE II. THE FIBERS SHRINK WHILE STILL IN THE PRESENCE OF THE SWELLING AGENT AND SUBSEQUENTLY THE FIBRES ARE RESTRETCHED TO 95-110% OF THEIR ORIGINALLENGHT BEFORE SWELLING. THEN WHILE MAINTAINING THESE DIMENSIONS THE FIBRES OR ROVINGS OR SILVERS ARE RINSED OR NEUTRALISED AND RINSED AND WHILE STILL MAINTAINING THESE DIMENSIONS ARE DRIED AT TEMPERATURES EXCEEDING 70*C. THE FIBRES OR SILVERS OR ROVINGS CAN BE GIVEN A RESIN FINISH AND THEY WILL NOT SHOW THE USUAL DEGRADATION OF PROPERTIES.

United States Patent 3,822,994 PREPARING CO'ITON MATERIAL WITH IM- PROVED TENSILE STRENGTH RETENTION PROPERTIES Ian J. de Boer, Pijnacker, and Herman Borsten, Voorschoten, Netherlands, assignors to Nederlandse Organisatie Voor Toegepast-Natuurweten-Schappelijk Onderzoek Ten Behoeve Van Nijverheid, The Hague, Netherlands No Drawing. Filed Jan. 28, 1972, Ser. No. 221,762 Claims priority, application Great Britain, Feb. 19, 1971, 4,982/71 Int. Cl. D06m N US. Cl. 8-125 4 Claims ABSTRACT OF THE DISCLOSURE Cotton fibres or rovings or slivers are subjected to the action of a swelling agent without tension being exerted on them. The swelling agent should be capable of transforming the material into cellulose II. The fibres shrink while still in the presence of the swelling agent and subsequently the fibres are restretched to 95-110% of their original length before swelling. flhen while maintaining these dimensions the fibres or rovings or slivers are rinsed or neutralised and rinsed and while still maintaining these dimensions are dried at temperatures exceeding 70 C. The fibres or slivers or rovings can be given a resin finish and they will not show the usual degradation of properties.

I- IE/IJD AND BACKGROUND OF INVENTION AND SPECIFICATION The invention concerns a method of preparing cotton fibres, slivers, or rovings which is based upon the application of definite swelling, stretching, rinsing, and drying treatments on fibres, slivers and rovings. The fibres obtained have a distinctly higher strength and 'an improved response to subsequent easy-care finishing.

In extreme circumstances the increase in fibre strength may amount to about 200% of the original strength.

if the treatment of the fibres is followed by a react-ant application using the usual methods, then at most only a small decrease of strength will be observed.

This fact is in contrast with the behaviour of untreated cotton which shows a strength decrease of 30-50% after the same reactant treatment.

The invention comprises the steps of swelling the cotton fibre or sliver or roving without tension in a swelling agent so as to obtain cellulose II as e.g.: caustic soda with a concentration of at least 512% NaOH, or preferably higher, e.g. 25% NaOH. Next the swollen, and thus strongly shrunk, material is stretched to -a level of '95115% of the original length in its caustic soda and further, if necessary, during rinsing. I

Finally the material is dried while maintaining the dimensions reached. The fibres or slivers or rovings obtained in this way are spun either in the wet or the dry state into weaving or knitting yarns.

Treating yarns by using the technique described is not recommended, because an essential change in the yarn structure involving a very low elongation of the yarn will occur. A reactant finishing process using the treated fibrous materials does not lead, or does so only to a small extent, a decrease of the strength properties of the fibres and yarns respectively of the fabrics and 'knittings prepared from these fibres and yarns.

Concerning the procedures used, the following remarks can be made.

To prevent slipping from occurring during the stretching treatments it is desirable to twist the slivers and rovings to such a degree that during stretching in the swelling "ice phase destruction of the yarn structure cannot occur, which means that the load applied is transferred to the fibres. On the other hand, it is not desirable to choose the degree of twist higher than is strictly necessary to prevent insufficient penetration of the material during the swelling phase. The shinkage occurring during swelling may be about IS- 20%.

The restrec'tching of the fibre or the sliver or the roving may be carried out by a conventional method, e.g. by stretching between two pairs of rollers, the second pair of which has a higher speed than the first pair. :In some cases use can be made of two clamps holding the yarn by enlarging the distance between them. The restrectching treatment should preferably start when the material is still completely swollen, as only then are the necessary high stretching levels easily obtained using relatively low loads at that time.

It is desirable to maintain the final stretching level in the caustic soda and during rinsing for 'at least 1-4 minutes.

If the caustic soda is removed completely before restretching it is very often impossible, even by applying large loads, to realize the desired degree of restretching. In general, material breakage will occur. The caustic soda should preferably be removed completely before the final drying treatment.

If a complete caustic removal cannot be reached before drying, the rinsing treatment may be repeated after drying.

Especially if the material is wet spun, twistless, followed by wet uptwisting so as to obtain a yarn, this method is less disturbing. [[f a dry spinning method is applied a complete removal of the caustic soda preceding drying is necessary.

It may be remarked, however, that traces of caustic soda and salts remaining in the dry fibrous material may have very unfavourable effects on the mechanical properties of the fibrous material.

During dry spinning it may be necessary to untwist the treated slivers or rovings before passing on to the final spinning treament. 'It is preferable that the drying treatment should be carried out in such a way that at least the final length reached during swelling and rinsing is maintained. Experience shows that imperfections caused during swelling as a consequence, e.g. of an imperfect penetration of the caustic soda into the material, may be nearly completely eliminated by using a high degree of restretching during the drying treatment. Thus, even fibres which are stretched insufiiciently show an essential improvement of the tensile properties if restretching is applied to as high a degree as possible. Subsequently, the drying treatment contributes quite essentially to the elfect which is desired. In fact, drying should lead to a setting of the structural changes introduced into the fibres by applying the treatments mentioned above. In order to obtain an almost ideal setting, the moisture should be removed as much as possible without damaging the fibre material thermally. Based upon experiments carried out, drying by means of infrared radiation meets the above-mentioned requirement.

However, it has appeared that other drying methods also lead to the results desired. On the basis of examples some aspects discussed will be illustrated. In the examples to be given use was made of different cotton varieties. It should be noted, however, that a mutual comparison of the results is not always proper.

EXAMPLE I Fibre treatments A bundle of cotton fibres was swollen without tension in 24% NaOH. After complete swelling the fibres were 3 restrectched to between 100% and 105% of the original length. Restretching was carried out during swelling and rinsing of the caustic soda. Their final dimensions reached during restretching were maintained for "at least one minute.

After a complete removal of the caustic soda from the fibres they were dried at l1-20 C. and/or conditioned at 65% relative humidity and C.

Next the conditioned material was finished using a reapparatus. Finally, the wet material was spun twistless. In order to obtain the best normal yarn possible, the twistless material was uptwisted in the moist state. To obtain comparable material an unmercerised roving was spun in the same way and uptwisted. In this way a 27 tex. yarn was made applying a twist of 700 turns per metre.

The results of a number of preliminary experiments during which different reactant quantities (Fixapret CPN) were used according to the usual method (example I) are actant having as a catalyst 'Mgcl in the amount of 7% 10 reproduced in Table 2.

of the reactant weight. The reactant solution was applied in a quantity equal to the weight of the fibres. After storage for one hour at room temperature and 100% relative humidity, the fibres were dried at 70 C. and then baked for 5 min. at 160 C.

After washing with 11% solution of neutral soap and rinsing, the fibres were conditioned again. The values obtained for the fibre strength of one cotton variety are compiled in Table 1. From this data it appears-that the described method leads to very strong fibres even after applying a reactant. Other cotton varieties lead to completely analogous results (see example IV), however, the actual strength increase reached may vary after the application of the reactant (example IV EXAMPLE III Fabric prepared from treated fibres From fibres treated as described in Example I, after spinning a plain weave fabric was woven having these specifications: warp 32 threads/cm; weft 31 threads/cm; 190 g./m. Subsequently, Fixapret CPN was applied to TABLE 1 [Tensile strength in grams] Without resin finish After resin finish Conditioned Dried at 120 C. Conditioned Dried at 120 0.

Main- Main- Main- Main- Without tained Without tained Without tained Without talned Pretreatment tension length tension length tension length tension length None. 6.0 6.0 6. 5 6. 5 4. 0 4. 0 4. 0 4. 0 Mercerized without tension and without aiter-stretchingu uu 8. 5 8. 5 9. 0 9.0 4. 5 4. 5 6. 5 4. 0 Mercerized without tension and with an after-stretching to 100% of the length before mercerization 9. 5 10. 0 10. 0 10. 5 7. 0 8. 5 10. 5 10. 0 Mercerized without tension and with an after-stretching to 105% of the length before mereerization 11.0 11. 5 10.0 11. 0 7. 5 l0. 5 9. 5 10. 5

EXAMPLE II Roving treatment Use was made of a hypochlorite bleached 300 tex. roving. The material consisted of the following industrial cotton mixture:

70% Columbia 25% Mozambique 5% Greek this fabric according to the directions of the manufacturer, thus including the usual additives.

All properties were measured on samples washed 5 times. With reference to Table 3, relating to some properties of the fabric, the following conclusions may be drawn.

The treated material shows a clearly greater strength when the reactant has been applied. Generally speaking the total elongation does not show large differences. The tearing strength of the reactant treated preswollen material is better and this tendency is more pronounced with an increasing reactant content.

The dry crease recovery angle of the preswollen material without reactant is somewhat higher than that of the blank material. When the reactant has been applied the differences disappear.

The wet recovery angles are nearly the same for blank and treated material.

TABLE 3 Non treated Treated Fixapret CPN (percent) 3 6 0 3 6 Fibre, yarn and fabric properties:

Fibre strength (g.) 3.7 2.0 1.9 6.4 6.6 4.9 Iglflongation at break (percent) 3. 6 2. 7 5. 4 4.2

Strength (g./tex.):

Warp 20.0 10.9 8 2 17.8 12. 1 10. 9 Weft 18.7 9.5 7 8 17. 6 12.6 12. 6 Elongation at break (percent):

Warp 7.3 4.0 4 1 5.5 3.3 4.2 Weft 6. 7 5. 4 3 4. 9 3. 9 4.1 Fabric:

Tensile strength (kg/5 0111.):

Warp 61 39 34 59 52 50 57 40 34 62 52 42 arp 57 114 142 67 111 135 Well; 47 110 136 61 105 127 Crease recovery angle (wet):

Warp 65 93 105 66 79 115 Weft 59 89 123 70 106 111 EXAMPLE IV d l h th h 3. Process accor in to c aim 1 w erein e stretc in Results using different cotton vaneties g g in the swelling agent and during the rinsing step lasts at least 1-4 minutes.

4. Process according to claim 1, wherein the swelling agent is completely removed before final drying of the material.

swelling the unrestrained material in a swelling agent to effect a transformation of the material to Cellulose II; stretching the material, in the presence of the swelling agent, to a length within 95 to 110 percent of the original length of the material before the soaking step, the stretched length being continuously maintained during the remaining steps in the process; rinsing the material while in the stretched condition to remove the swelling agent; and drying the material while in the stretched condition at a temperature in excess of 70 C. to set the improved tensile strength properties obtained. 2. Process according to claim 1 wherein the swelling agent is an aqueous solution of sodium hydroxide with a strength of 12-24% NaOH.

TABLE 4 Blank material Treated material Relative fibre strength Fibre Elonga- Fibre Elongawith strength tion strength tion res ect (g.) (percent) (g.) (percent) to b ank Acala 1517 6. 0 8. 0 13. 0 5. 5 2.0 Pakistan dessi 8.0 11.0 16. 0 7. 0 2. 0 Russian Pervyi. 4. 0 11.0 6. 5 6.5 1.6 Sudan 6 G L 3. 5 8.0 9.0 6.0 2.0 Peruvian Tangui 6. 5 12. 5 10. 0 7. 0 1- 8 Uganda 2. 5 10. 5 5. 0 a. 5 2.0 Turkish Amana 4. 0 7. 5 6. 5 6. 5 1. 6 Deltapine (American) 3.5 10.0 7.0 7.0 2.0

From this data it appears, that the treatment applied led References Cited in all cases to a relatively very high fibre strength while UNITED STATES PATENTS a high elongation at break level Was maintained. 1,901,095 3 1933 Goldthwait g. What is claimed is: 50 2,205,120 6/1940 Heberlein, Jr. et a1. 8-125 X 1. A process for preparing a cotton material selected 3498739 3/1970 Murphy et 8 125 from the group consisting of cotton fibres, slivers and rov- FOREIGN PATENTS ings with improved tensile strength retention properties 612,745 11/ 1948 Great Britain 8-125 "misting 55 OTHER REFERENCES Warwicker, et al.: A Review of the Literature on the Effect of Caustic Soda and Other Swelling Agents on the Fine Structure of Cotton, Shirley Inst. Pamphlet No. 93, The Cotton Silk and Man-made Fibres Research Assn., Shirely Inst., Didsbury, Manchester; December 1966, Title page and pages 96-98.

ASTM Designation: D2256-69-Standard Method of Test for Breaking Load (Strength) and Elongation of Yarn by the Single-Strand MethodAmerican National Standard L14189-1970, American National Standards Inst; 1970, pages 380-387.

Dipl.-Ing. 0. Becker (Institut fur Textile Messtechnik M.-Gladbach E. V.): Prufge-Rate zer Bestimmung der Festigkeit und Dehnung von Einzelfasern, Textil-Praxis; May 1959, pages 443-449.

RICHARD D. LOVERING, Primary Examiner US. Cl. X.R.

8-495, Dig. 3; 571-64; 161-411 3 533 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIN Patent 3.822.994 Dated 9, 974

9 Inventor(s) Jan J. de Boer and Herman Borsten It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 52, ."25%" should read -24%;

line 54, "the" should read -itsand "its" should read the'-; line 61, "recemmended" should read recommended;

' line 65, "a decrease"- should read --to a decrease-;

Column 2, line 13, "strestrectching" should read -restretchi:ng--;

and

Column 3, line 1, "restrectched" should read --res'tretched- 9 This certificate supersedes Certificate of Correction issued December 3, 1974.

Signed and Scale this 6 Tenth Day of August 1976 [SEAL] Arrest:

@ RUTH C. MASON C. MARSHALL DANN AM -"m8 Office Commissioner oj'Patem: and Trademarks mg UNITED STATES PATENT OFFICE CER TIFICA'IE OF CORRECTION Patent No. 3, 822 994 Dated July 9 1974- Inveri tor(s)-Jan J. de Boer and Herman Borslten It is certified that error a p p ears in the a bdvewid' e fiti f ied p ate nt I and that said Letters Patent are hereby corrgcted as ShOWfl'bElOWK Column l, 11n e 52, .25%" shouldr ead --2.4'%--:,f-' 1 "reaa the--; Q p

line' 61, ".recemmended shouldread' --recomm ended'f'fi line 65, "a decrease" should ready-etc a decrease-+ Column 2, line 13, "stres'trectching'i should read -restre1 :ch1ng-;

' Column 3, line 1, "restrectched" should read; -i--restre1 :ch ed Y sigr l i'edfg ridrsealed this" 3rd lay of De c f e 'x ixt jr 19174.

(SEAL) Attesrr McCOY M.'c1'nsbi-f JR. c; 'MARsHAL-L DANN Arresting Officer 1 Commissioner "bf Patents 

